replace all "foo" between ()

Question

I've problem with my regex code, the problem is: I want to replace all "foo" values but only inside "()". Example:

try foo foo-foo (try foo inside , foo foo foofoo)

I want to replace all "foo" strings between the parentheses by "boo".

Answer 1

Assuming parentheses are "valid", you can replace all foos that are followed by ), without a ( in between:

$str = preg_replace('/foo(?=[^()]*\))/', 'bar', $str);

Working example: http://ideone.com/xezU7

Another option, also assuming no nested pairs, is to match "(...)" tokens and use a callback, but it may be use of excessive force:

Callback method:

function replace_foo($matches) {
   return str_replace('foo', 'bar', $matches[0]);
}

use:

$str = preg_replace_callback("/\([^()]*\)/","replace_foo", $str);

Working example: http://ideone.com/ZzBem